Hello Willi,
As Sandy said, this is the first time I've seen such an eagle. It's an M71 (vVv tail) for infantry (abdomen feathers vertical, not V-shaped) but with worked head screws like on the M42s.
I---Here's the eagle this helmet should have, if it still has the screw heads modified in 1862.
View attachment 52362
2---Here's the November 1860 eagle for the Cuirassiers:
iIi tail feathers and V-shaped belly feathers. This M60 model is the same design for both infantry and cuirassiers. However, it remained for cuirassiers until the M15 model in gray iron, while in 1867-71 the infantry was given a new eagle.
View attachment 52363
View attachment 52364
3---And here's the M67 or 71 infantry eagle with vertical belly feathers and vVv tail feathers.
View attachment 52365
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View attachment 52367
The part circled in blue doesn't fit because it doesn't correspond to the cuirassier eagle model.
In addition, I've never seen such an eagle on the Vaterland-Bandeau.
A trial eagle??? not adopted?